Some of inkjet printers perform printing of a desired character, figure, pattern, photograph or the like on a printing medium by ejecting ultraviolet curing type ink having property of being cured by irradiating ultraviolet rays (hereinafter, referred to as “UV” ink) from an inkjet head. The “UV” ink is superior in weather resistance and water resistance and thus, the printed object can be used, for example, as an outdoor advertisement bill or the like and a usable application of the printed object is remarkably expanded in comparison with a case that water-soluble ink is used. As described above, an inkjet printer in which printing is performed by ejecting “UV” ink is provided with an ultraviolet irradiation device for irradiating ultraviolet rays to the “UV” ink that is stuck to a printing medium so as to cure the “UV” ink. Recently, an inkjet printer (see, for example, Japanese Patent Laid-Open No. 2004-188920) has been developed and practically used in which an ultraviolet light emitting diode (hereinafter, referred to as a “UVLED”) is used as a light source for emitting ultraviolet rays (hereinafter, referred to as a “UV” light source) in the ultraviolet irradiation device.